The present invention relates to an ultra-thin pump and a cooling system including the pump.
To meet a recent demand for a cooling system for cooling an electronic device, such as a CPU, efficiently, a cooling system using circulation of coolant has received attention. The miniaturization of the electronic device entails many limitations of space for a coolant circulation pump used in such a cooling system. Accordingly, miniaturization and reduction of thickness are strongly demanded of the pump.
Conventional small-size pumps include a small-size centrifugal pump such as disclosed in Japanese Unexamined Patent Publication No. 2001-132699. This conventional small-size centrifugal pump is described hereinafter with reference to FIG. 15. Impeller 101 is rotatably supported by stationary shaft 102. Pump casing 103 secures ends of shaft 102, houses impeller 101 and defines a pump chamber for recovering pressure from kinetic energy imparted to fluid by impeller 101 and directing the fluid to discharge port 110. Impeller 101 is constructed of back shroud 104 and front shroud 105 having a suction opening in the center of impeller 101. Rotor magnet 106 is fixed to back shroud 104, and motor stator 107 is provided in a space enclosed by an inner surface of rotor magnet 106. Bulkhead 108 is provided between rotor magnet 106 and motor stator 107 for sealing the pump chamber. Pump casing 103 also includes suction port 109 and discharge port 110.
An operation of this conventional centrifugal pump is described as follows. When electric power is supplied from an external power source, current controlled by an electric circuit provided at the pump flows through coils of motor stator 107, which in turn generates a rotating magnetic field. This rotating magnetic field acts on rotor magnet 106 to impart physical force (rotational torque) to magnet 106. Since impeller 101 secures this rotor magnet 106 and is rotatably supported by stationary shaft 102, the rotational torque acts on impeller 101, whereby impeller 101 starts to rotate. Vanes provided between front and back shrouds 105, 104 change momentum of the fluid during the rotation of impeller 101. The fluid flowing in from suction port 109 receives the kinetic energy from impeller 101 and is directed to discharge port 110. The conventional centrifugal pump is small in size and low-profile because the outer rotor is used to drive the low-profile impeller, as described above. However, there is a limit to further reduction of the thickness of the centrifugal pump due to the structure of the impeller or the like.
On the other hand, a regenerative pump can be easily reduced in thickness. However, the conventional regenerative pump has various problems.
One of the particular problems is that the life of the regenerative pump is hard to extend due to the pump""s durability to withstand radial load-induced friction at a rotating part and thrust load-induced friction between the impeller and the pump casing during the rotation of the impeller. The other problems include problems of higher efficiency and further reduction in thickness that are attributable to the structure of the regenerative pump.
An ultra-thin pump of the present invention includes:
a ring-shaped impeller including a plurality of vanes arranged along its outer region, and a rotor magnet at its inner region;
a motor stator provided in a space encircled by an inner peripheral surface of the rotor magnet of the impeller; and
a pump casing for housing the impeller, the pump casing including a suction port, a discharge port and a cylinder disposed between the motor stator and the rotor magnet,
wherein the impeller is rotatably supported by the cylinder.
A cooling system of the present invention includes:
a cooling device for cooling a heat-producing device by heat exchange using a coolant;
a radiator for removing heat from the coolant; and
an ultra-thin pump for circulating the coolant.